• 전력전자학회논문지
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• 제6권1호
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• pp.34-42
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• 2001

전지는 화학에너지를 기계적인 처리과정 없이 전기에너지로 직접 전환하는 장치이다. 부하전압과 부하전류의 용량에 따라 단위전지를 직.병렬 연결하여 사용하게 되며, 전지의 병렬운전은 단독운전 보다 전압강하를 더 천천히 발생시키므로 전압강하에 민감한 전력변환장치들의 효율에 밀접한 관계를 가지고 있다. 병렬운전의 필요성과 장점 때문에 대부분의 축전지를 사용하는 시스템은 병렬운전을 하고 있고, 반면에 선.구 축전지 사이에서 순환 전류가 흐르고, 자가방전이 일어나는 단점 또한 가지고 있다. 신 축전지에서 충.방전 전류가 과다하게 흐르는 불평형 현상과 이로 인해 축전지의 수명단축을 일으키게된다. 본 논문에서는 마이크로 프로세서를 사용하여 선.구 축전지 사이의 볼평형 전류를 검출하고 외부저항을 첨가시켜 내부저항의 차이에 대한 감소효과를 얻어 불평형 전류를 보상하였다. 이를 실험을 통해 구현하였다.

• 전력전자학회논문지
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• 제20권6호
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• pp.517-525
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• 2015

A grid connected inverter must be operated as the main electricity source under an isolated condition caused by the grid problem. Conventionally, the dual loop controller is used for the grid inverter, and the controller is used for control under the stand-alone mode. Generally, the PI(Proportional - Integral) controller is highly efficient under a synchronous reference frame, and stable control can be available. However, in this synchronous frame-based control, high-quality DSP is required because many sinusoidal calculations are necessary. When the PI control is conducted under a stationary frame, the controller constructions are made simple so that they work even with a low-price micro controller. However, given the characteristics of the PI controller, it should be designed with the phase of reference voltage considered. Otherwise, the phase delay of the output voltage can occur. Although the current controller also has a higher bandwidth than the voltage controller, distortion of the voltage is difficult to avoid only by the rapid response of the PI controller, as a sudden load change can occur in the nonlinear load. In this study, a new control method that solves the voltage controller bandwidth problem and rapidly copes with it even in the nonlinear load situation is proposed. The validity of the proposed method is proved by simulation and experimental results.

• 한국통신학회논문지
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• 제33권2A호
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• pp.204-209
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• 2008

교통정보 시스템에 있어서 가장 중요한 것은 각 도로의 교통상황이나 유고정보 등 Event를 얼마나 빨리 전달하느냐에 달려있다. Event 정보를 TPEG 시스템에서 보다 효과적으로 운영하기 위해서는 효과적인 전달 시스템이 필요하기 때문에, 본 논문에서 개선된 전달 시스템을 제안하려고 한다. 개선된 전달 시스템은 교통정보 데이터를 TPEG 데이터로 변환한 후에 단순하게 FIFO 방식을 이용하여 전달하는 기존의 방식과는 달리 교통정보의 우선순위를 고려한다. 제안하는 우선순위 기반의 방식은 어떤 정보가 중요한 교통정보인가 판별한 후에 우선순위에 따라 스케줄링 하여, 중요한 정보는 보다 빨리 전달이 되도록 하고 또한 우선순위에 따라 전송 주기를 앞당긴다. 한편, 중요도가 낮은 교통정보는 늦게 전달이 이루어지며 우선순위가 낮으므로 전송주기도 늦어지게 된다. 컴퓨터 시뮬레이션을 통하여 제안하는 방식이 갑작스런 교통상황의 변화와 중요한 교통정보를 보다 빨리 전달할 수 있다는 것을 보여주고 있다.

• 한국기록관리학회지
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• 제18권3호
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• pp.1-24
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• 2018

최근 한반도를 둘러싼 국제 정세가 급변하고 있다. 평창올림픽 개최 전까지만 해도 경색 국면이었던 남북관계가 해빙무드로 전환되어 사회 전반에 걸쳐 통일에 대한 기대감이 고조되고 있으나 한편으로 북한의 전통적인 화전양면(和戰兩面) 전술을 경계해야 한다는 경계의 목소리도 공존하고 있다. 최근 조사에서 드러난 대학생과 청소년층의 낮은 안보의식은 국민들의 확고한 안보의식과 국가관 확립의 필요성을 보여준다. 이를 위해 국가안보의 핵심기관인 육군이 소장한 각종 기록(Army Records)을 온라인 콘텐츠로 재창출하여 제공하는 것이 하나의 방편이 될 수 있다. 본 연구에서는 우방국이자 기록관리 선진국으로 평가받는 미 육군 아카이브즈의 온라인 콘텐츠 서비스 현황을 살펴봄으로써 우리 군 기록의 온라인 콘텐츠 서비스 발전방안을 제시하고자 한다.

• 한국정보시스템학회지:정보시스템연구
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• 제29권2호
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• pp.131-147
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• 2020

Purpose The purpose of this study is to develop intelligent vehicle parking distribution system based on LoRa network at the circumstance of traffic congestion during cultural festival in a local city. This paper proposes a parking dispatch and distribution system using a Q-learning algorithm to rapidly disperse traffics that increases suddenly because of in-bound traffics from the outside of a city in the real-time base as well as to increase parking probability in a parking lot which is widely located in a city. Design/methodology/approach The system get information on realtime-base from the sensor network of IoT (LoRa network). It will contribute to solve the sudden increase in traffic and parking bottlenecks during local cultural festival. We applied the simulation system with Queuing model to the Yudeung Festival in Jinju, Korea. We proposed a Q-learning algorithm that could change the learning policy by setting the acceptability value of each parking lot as a threshold from the Jinju highway IC (Interchange) to the 7 parking lots. LoRa Network platform supports to browse parking resource information to each vehicle in realtime. The system updates Q-table periodically using Q-learning algorithm as soon as get information from parking lots. The Queuing Theory with Poisson arrival distribution is used to get probability distribution function. The Dijkstra algorithm is used to find the shortest distance. Findings This paper suggest a simulation test to verify the efficiency of Q-learning algorithm at the circumstance of high traffic jam in a city during local festival. As a result of the simulation, the proposed algorithm performed well even when each parking lot was somewhat saturated. When an intelligent learning system such as an O-learning algorithm is applied, it is possible to more effectively distribute the vehicle to a lot with a high parking probability when the vehicle inflow from the outside rapidly increases at a specific time, such as a local city cultural festival.

• 대한간호학회지
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• 제48권5호
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• pp.601-621
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• 2018

Purpose: This study aimed to synthesize the caring experiences of Korean family members of patients with dementia through a qualitative meta-synthesis method. Methods: By searching through nine Korean and English databases, we compared 37 qualitative studies on caring experiences of family members of patients with dementia. The selected studies were synthesized through meta-synthesis, proposed by Sandelowski and Barroso (2007). Results: The meta-synthesis elicited four themes: tough life due to care for patients, changes in relationships, adaptation to caregiver's roles, and new perspectives of life through personal growth. Caregivers were shocked when a sudden diagnosis of dementia was made prior to any preparation on their part. They were tied to their patients all the time and their mind and body got exhausted. Their relationship with patients began to change and they looked at them differently. They experienced conflicts with the other non-caring family members and were alienated from them. They were also socially isolated. However, by building their own care strategies and utilizing social resources, they gradually adapted to their caregiver roles. Finally, they experienced personal growth and acquired a new perspective toward life by accepting their roles and finding meaning in their lives. Shifting the caregiver's centricity from themselves to the patient was the process of becoming human beings who actively constructed their realities while giving meaning to their painful lives and interacting with the environment. Conclusion: The results of the study can be useful for nurses in understanding the experiences of caregivers of the patients with dementia and in providing them with practical interventions.

• 대한안전경영과학회지
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• 제16권2호
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• pp.217-230
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• 2014

The purpose of this study is to develop the Generalized Depreciation Function (GDF) and Winfrey Depreciation Function (WDF) by reviewing methods for the depreciation accountings. The Depreciation Accounting Models (DAM), including straight-line model, declining-balance model, sum-of-the-year-digit model and sinking fund model presented in this paper, are reclassified into the charging pattern of increasing type, decreasing type and constant type. This paper also discusses the development of the GDFs based on convex type, concave type and constant type according to the demand pattern of product, frequency of plant usage, deterioration of time, relative inadequacy, Capital Expenditure (CAPEX) and Operating Expenditure (OPEX) of the Total Productive Maintenance (TPM). The WDFs presented in this paper depict a sudden degradation of plant performance by measuring the change of TPM activity at the midpoint of useful life of asset. The WDFs are classified into left-modal type, symmetrical type and right-modal type by varying the value of skewness and kurtosis. Moreover, three increasing patterns, such as convex, concave and linear types, are used in this paper to present the distinct identification of WFDs by using Instantaneous Depreciation Rate (IDR) in terms of Performance Depreciation Function (PDF) and Depreciation Density Function (DDF). In order to have better understanding of depreciation models, the numerical examples are used for evaluating the Net Operating Less Adjusted Tax (NOPLAT) and Economic Value Added (EVA). It is concluded that the depreciation models showing a large dispersion of EVA require the adjustment of NOPLAT and Invested Capital (IC) based on the objective cash basis and net operating activity for reducing the variation of EVA.

• Nuclear Engineering and Technology
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• 제26권2호
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• pp.225-236
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• 1994

SEBIM 밸브 상부에 위치한 밀봉수의 급격한 방출은 밸브 후단의 방출배관계통에 큰 운동량과 관성력의 작용을 초래한다. 본 연구는 밸브개방시 방출배관계통의 후단에 발생하는 열수력학적 과도현상을 분석하기 위한 해석절차 및 해석결과를 다루고 있으며, 이 분석을 위해 RELAP5 /MOD3 를 사용하였다. RELAP5 /MOD3 분석을 위하여, 방출관 계통과 SEBIM 밸브의 개방특성 및 밀봉수 방출등의 적절한 모델방법이 제시되었다. 또한 접합부(junction)와 체적(volume)의 제어 플래그 (flag)에서 옵션(option)의 적절한 선택을 위하여 민감도분석도 수행되었다. 분석결과, SEBIM 밸브 방출배관계통의 밀봉수 방출에 따른 열수력학적 과도현상을 분석하는데 RELAP5 /MOD3가 적절히 사용될 수 있음을 알 수 있었다. 민감도 분석결과로부터, 밀봉수 방출해석을 위해서는 적절한 기하학적 압력분포를 가지는 완만한(smooth) 면적변화 및 비평형 옵션(option), 적절한 시간간격(time step)의 사용이 필수적인 것을 알 수 있었다.

• 동굴
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• 제68호
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• pp.5-22
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• 2005

Since earlier in 1947 the writer had been devoting part of his time to study alluvial fans in Korea based on his own interest in geomorphology. However, it was in 1958 when a new geography department was set up and the Research Center of National Lands was established in the university of Kyung Hee, the writer started scientific investigation for alluvial fans. The Following alluvial fans have been studied by the writer: those of Mt. Kwanak and Mt. Chungge in 1947; those of Pulkuksa in 1948; those of Suhnamsa, Suh Myun, Pusan in 1950; those of Shindonae, Mt. Kerrong, in summer of 1958; those of Hwaomsa, Kure and Yongsan Myun, Changhung, in winter of 1958. The article is the comparative study of the above mentioned alluvial fans including Suhkwangsa Fan, Chugaryng Rift Valley. Of course this is not the study covering all af alluvial fans in Korea. Within the limits of his surbey, the writer has com to a conclusion which may be helpful for the Korean alluvial fm study. 1. Korean alluvial fans are generally found in rift valleys or basins. 2. They are formed in places of below 220-meter contour line. 3. The slope from fna apex to river valley is 20-40 degree. The slope of fan surface is 5-20 degree, but most of them under 16 degree. A sudden change of slope is taken place or the fan apex and fan center. 4. Hills (100-200m) are developed on the surfaces of alluvial fans. 5. Most of rivers in alluvial fans are geyser rivers. 6. The depth of well : from ground surface to the well water surface is 4-8 m; water depth is 1-2m. 7. Land utilization; cultivated land 30%: non cultivatedland 70%. The area occupied by upland fields is twice of paddy field area. 8. Settlement : agglomerated settlement is developed on the top or the end of fan and surrounded by windbreakers. 9. Farming pattern at the top of fan fields are rectangular and parallel to flumes but at the center of fan, they are irregular and perpendicular to flumes.

• 조명전기설비학회논문지
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• 제25권8호
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• pp.8-19
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• 2011

This paper was compared for the output voltage and efficiency of the single-phase Z-source inverter(ZSI) according to shoot through duty ratio D. The eight single-phase ZSI in this study are typical ZSI, Embedded ZSI(EZSI), Improved ZSI(IZSI), Quasi ZSI(QZSI), Series ZSI, Trans ZSI(TSI), Switched inductor ZSI(SL-ZSI) and Extended boost ZSI (exZSI). The eight ZSI are divided into two Groups. ; Group-1 which is ZSI with the ordinary voltage boost factor B, and Group-2 which is ZSI with the maximum voltage boost factor B. For the execution of the proposed study, the PSIM simulation was achieved under the condition of input DC voltage=150[V] of ZSI, load =30[${\Omega}$] and 60[Hz] output filter. The output voltage and efficiency of each ZSI were calculated within the limits of D=0.1~0.4. As a result, the output peak voltage of Group-2 was suddenly increased in a specified duty ratio D, and its efficiency was rapidly decreased. On the contrary, Group-1 shown the output and efficiency characteristics without sudden change compared to Group-2 despite the duty ratio increase. The efficiency of the Group-2 was sharply declined at duty ratio D of the most output voltage, but, in case of Group-1, the efficiency was slightly declined. Finally, the input DC current of ZSI with DCM and CCM was discussed.